®
Preliminary
SP6137HV
Dual Supply Synchronous Buck Controller
FEATURES
■
■
■
■
■
■
■
■
■
■
■
3V to 28V Step Down Achieved Using Dual Input
Small 10-Pin MSOP Package
2A to 15A Ouput Capability
Highly Integrated Design, Minimal Components
UVLO Detects Both V
CC
and V
IN
Short Circuit Protection with Auto-Restart
On-Board 1.5Ω sink (2Ω source) NFET Drivers
Programmable Soft Start
Fast Transient Response
High Efficiency: Greater than 94% Possible
A Synchronous Start-Up into a Pre-Charged Output
V
CC
1
GL
2
GND
3
V
FB
4
COMP
5
10
BST
SP6137H
10 Pin MSOP
9
GH
8
SWN
7
SS
6
UVIN
Now Available in Lead Free Packaging
APPLICATIONS
■
12V DPA
■
Communications Systems
■
Graphics Cards
DESCRIPTION
The SP6137HV is a synchronous step-down switching regulator controller optimized for high efficiency. The part is
designed to be especially attractive for dual supply, 12V step down with 5V used to power the controller. This lower V
CC
voltage minimizes power dissipation in the part. The SP6137HV is designed to drive a pair of external NFETs using a
fixed
900kHz
frequency, PWM voltage mode architecture. Protection features include UVLO, thermal shutdown and
output short circuit protection. The SP6137HV is available in the cost and space saving 10-pin MSOP
.
TYPICAL APPLICATION CIRCUIT
VIN
3.5V - 28V
C1
22µF
16V
FDS6676S
14.5A, 6mΩ
1 2 3
8 7 6 5
C2
22µF
16V
GND
V
CC
= 5V @ 30mA
QT
4
RLF
3.0,5%
CBST
1µF
DBST
MBR0530
1
C1, C2
Ceramic
1210
X5R
U1
SP6137H
VCC
GL
GND
VFB
COMP
BST 10
GH 9
SWN 8
SS 7
UVIN 6
2
3
4
0.8V
5
R5
Bead
8 7 6 5
R3
221k, 1%
UV
IN
R4
100k, 1%
C
VCC
10µF
6.3V
C
VCC
Ceramic
8050
X5R
RZ3
4.64k, 1%
C3
47µF
6.3V
C4
47µF
6.3V
CZ3
220pF
V
OUT
≤
VIN
0.8V - 3.3V
0 - 10 A
R1
68.1k, 1%
GND 3
QB
4
SS
CSS
47nF
1 2 3
FDS6676S
14.5A, 6.0mΩ
CZ2
RZ2
GND2
C3, C4
Ceramic
1210
X5R
V
OUT
=(R1/R2 +1)V
FB
820pF 40.2k, 1%
CP1
CF1
100pF
56pF
fs=900Khz
R2
21.5k, 1%
Date: 5/25/04
SP6137HV Dual Supply, Synchronous Buck Controller
© Copyright 2004 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at
these ratings or any other above those indicated in the operation sections
of the specifications below is not implied. Exposure to absolute maximum
rating conditions for extended periods of time may affect reliability.
V
CC
.................................................................................................. 7V
BST ............................................................................................... 22V
BST-SWN ......................................................................... -0.3V to 7V
SWN ................................................................................... -1V to 15V
GH ......................................................................... -0.3V to BST+0.3V
GH-SWN ......................................................................................... 7V
All other pins .......................................................... -0.3V to V
CC
+0.3V
Peak Output Current < 10us
GH,GL ............................................................................................. 2A
Storage Temperature .................................................. -65°C to 150°C
Power Dissipation .......................................................................... 1W
Lead Temperature (Soldering, 10 sec) ...................................... 300°C
ESD Rating .......................................................................... 2kV HBM
Thermal Resistance ............................................................. 41.9°C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified: 0°C < T
AMB
< 70°C, 4.5V < V
CC
< 5.5V, BST=V
CC
,SWN = GND = 0V, UVIN = 3.0V, CV
CC
= 10µF,
C
COMP
= 0.1µF, CGH = CGL = 3.3nF, C
SS
= 50nF, Typical measured at V
CC
=5V. The
♦
denotes the specifications which
apply over the full operating temperature range, unless otherwise specified.
PARAMETER
QUIESCENT CURRENT
V
CC
Supply Current
BST Supply Current
PROTECTION: UVLO
V
CC
UVLO Start Threshold
V
CC
UVLO Stop Threshold
V
CC
UVLO Hysteresis
UVIN Start Threshold
UVIN Stop Threshold
UVIN Hysteresis
ERROR AMPLIFIER REFERENCE
Error Amplifier Reference
Error Amplifier Reference
Over Line and Temperature
Error Amplifier Transconductance
Error Amplifier Gain
COMP Sink Current
COMP Source Current
V
FB
Input Bias Current
Internal Pole
COMP Clamp
COMP Clamp Temp. Coefficient
Ramp Amplitude
RAMP Offset
RAMP Offset Temp. Coefficient
GH Minimum Pulse Width
Maximum Controllable Duty Ratio
Maximum Duty Ratio
Internal Oscillator Frequency
MIN
TYP
1.5
0.2
MAX
3
0.4
4.5
4.4
2.65
2.35
UNITS
mA
mA
V
V
mV
V
V
mV
♦
CONDITIONS
V
FB
=0.9V (No switching)
♦
V
FB
=0.9V (No switching)
4.00
3.80
2.3
2.0
4.25
4.05
200
2.5
2.2
300
♦
♦
♦
♦
0.792
0.788
0.800
0.800
6
60
150
150
50
4
2.5
-2
0.808
0.812
V
V
♦
2X Gain Config., Measure COMP/2
ms
dB
µA
µA
200
nA
MHz
V
mV/°C
1.28
V
V
mV/°C
180
ns
%
%
♦
♦
♦
♦
No Load
V
FB
= 0.9V, COMP = 0.9V
V
FB
= 0.7V, COMP = 2.2V
V
FB
= 0.8V
V
FB
=0.7V, T
A
= 25°C
CONTROL LOOP: PWM COMPARATOR, RAMP & LOOP DELAY PATH
0.92
1.1
1.1
-2
90
92
100
840
810
900
900
960
940
97
T
A
= 25°C, RAMP COMP
until GH starts switching
Maximum Duty Ratio Measured just
before pulse skipping begins
Valid for 20 Cycles
kHz
♦
Date: 5/25/04
SP6137HV Dual Supply, Synchronous Buck Controller
© Copyright 2004 Sipex Corporation
2
ELECTRICAL SPECIFICATIONS: Continued
Unless otherwise specified: 0°C < T
AMB
< 70°C, 4.5V < V
CC
< 5.5V, BST=V
CC
,SWN = GND = 0V, UVIN = 3.0V, CV
CC
= 10µF,
C
COMP
= 0.1µF, CGH = CGL = 3.3nF, C
SS
= 50nF, Typical measured at V
CC
=5V. The
♦
denotes the specifications which
apply over the full operating temperature range, unless otherwise specified.
PARAMETER
TIMERS: SOFTSTART
SS Charge Current:
SS Discharge Current:
Short Circuit Threshold Voltage
Hiccup Timeout
Number of Allowable Clock Cycles
at 100% Duty Cycle
Minimum GL Pulse After 20 Cycles
Thermal Shutdown Temperature
Thermal Recovery Temperature
Thermal Hysteresis
OUTPUT: NFET GATE DRIVERS
GH & GL Rise Times
GH & GL Fall Times
GL to GH Non Overlap Time
SWN to GL Non Overlap Time
GH & GL Pull Down Resistance
MIN
TYP
10
MAX
UNITS
µA
mA
♦
CONDITIONS
1
0.2
0.25
100
20
0.5
145
135
10
35
30
45
20
50
50
40
70
30
0.3
♦
Fault Present, SS = 0.2V
Measured V
REF
(0.8V) - V
FB
V
FB
= 0V
V
FB
= 0.7V
V
FB
= 0.7V
PROTECTION: SHORT CIRCUIT & THERMAL
V
ms
Cycles
Cycles
°C
°C
°C
ns
ns
ns
ns
KΩ
♦
♦
♦
♦
♦
Measured 10% to 90%
Measured 90% to 10%
GH & GL Measured at 2.0V
Measured SWN = 100mV to GL = 2.0V
PIN DESCRIPTION
PIN #
1
2
3
4
PIN NAME DESCRIPTION
V
CC
Bias Supply Input. Connect to external 5V supply. Used to power internal circuits and
low side gate driver.
GL
High current driver output for the low side NFET switch. It is always low if GH is high or
during a fault. Resistor pull down ensure low state at low voltage.
GND
Ground Pin. The control circuitry of the IC and lower power driver are referenced to this
pin. Return separately from other ground traces to the (-) terminal of C
OUT
.
V
FB
Feedback Voltage and Short Circuit Detection pin. It is the inverting input of the Error
Amplifier and serves as the output voltage feedback point for the Buck Converter. The
output voltage is sensed and can be adjusted through an external resistor divider.
Whenever V
FB
drops 0.25V below the positive reference, a short circuit fault is detected
and the IC enters hiccup mode.
COMP
Output of the Error Amplifier. It is internally connected to the non-inverting input of the
PWM comparator. An optimal filter combination is chosen and connected to this pin and
either ground or V
FB
to stabilize the voltage mode loop.
UVIN
UVLO input for V
IN
voltage. Connect a resistor divider between V
IN
and UVIN to set
minimum operating voltage.
SS
Soft Start. Connect an external capacitor between SS and GND to set the soft start rate
based on the 10µA source current. The SS pin is held low via a 1mA (min) current during
all fault conditions.
SWN
Lower supply rail for the GH high-side gate driver. Connect this pin to the switching node
at the junction between the two external power MOSFET transistors.
GH
High current driver output for the high side NFET switch. It is always low if GL is high or
during a fault. Resistor pull down ensure low state at low voltage.
BST
High side driver supply pin. Connect BST to the external boost diode and capacitor as
shown in the Typical Application Circuit on page 1. High side driver is connected between
BST pin and SWN pin.
SP6137HV Dual Supply, Synchronous Buck Controller
© Copyright 2004 Sipex Corporation
5
6
7
8
9
10
Date: 5/25/04
3
FUNCTIONAL DIAGRAM
5 COMP
100% Protection Logic
PULSES CLR
COUNT 20
CLOCK
FAULT
CLK
RESET
DOMINANT
10 BST
VCC
Gm ERROR AMPLIFIER
VPOS
VCC
10
µA
SS 7
SOFTSTART INPUT
POS REF
VCC
FAULT
Gm
PWM LOOP
VFBINT
9 GH
SYNCHRONOUS
DRIVER
8 SWN
2 GL
FAULT
VFB
R
Q
S
900 kHZ
QPWM
RAMP = 1.1V
FAULT
0.4 V
CLK
CLOCK PULSE GENERATOR
SS
REFERENCE
CORE
GL HOLD OFF
0.8V
REF OK
V
CC
1
1.7 V
1.7 V
ASYNC. STARTUP
COMPARATOR
3 GND
THERMAL
SHUTDOWN
145 ˚C ON
135 ˚C OFF
SET
DOMINANT
S
VPOS
VFBINT
0.25 V
+-
SHORT CIRCUIT
DETECTION
+
-
Q
HICCUP FAULT
FAULT
REF OK
R
VCC
+
4.25 V ON
4.05 V OFF -
+
2.50 VON
-
2.20 V OFF
VCC UVLO
POWER FAULT
VIN UVLO
CLK
COUNTER
200ms Delay
6
UVIN
CLR
REF OK
THERMAL AND SHORT CIRCUIT PROTECTION
UVLO COMPARATORS
THEORY OF OPERATION
General Overview
The SP6137HV is a fixed frequency, voltage
mode, synchronous PWM controller optimized
for high efficiency. The part has been designed
to be especially attractive for split plane applica-
tions utilizing 5V to power the controller and 3V
to 12V for step down conversion.
The heart of the SP6137HV is a wide bandwidth
transconductance amplifier designed to accom-
modate Type II and Type III compensation
schemes. A precision 0.8V reference present on
the positive terminal of the error amplifier per-
mits the programming of the output voltage
down to 0.8V via the V
FB
pin. The output of the
error amplifier, COMP, compared to a 1.1V
peak-to-peak ramp is responsible for trailing
edge PWM control. This voltage ramp and PWM
control logic are governed by the internal oscil-
lator that accurately sets the PWM frequency to
600kHz.
Date: 5/25/04
The SP6137HV contains two unique control
features that are very powerful in distributed
applications. First, asynchronous driver control
is enabled during start up to prohibit the low side
NFET from pulling down the output until the
high side NFET has attempted to turn on. Sec-
ond, a 100% duty cycle timeout ensures that the
low side NFET is periodically enhanced during
extended periods at 100% duty cycle. This guar-
antees the synchronized refreshing of the BST
capacitor during very large duty ratios.
The SP6137HV also contains a number of valu-
able protection features. A programmable input
(V
IN
) UVLO allows a user to set the exact value
at which the conversion voltage is at a safe point
to begin down conversion, and an internal V
CC
UVLO ensures that the controller itself has
enough voltage to properly operate. Other pro-
© Copyright 2004 Sipex Corporation
SP6137HV Dual Supply, Synchronous Buck Controller
4
THEORY OF OPERATION: Continued
tection features include thermal shutdown and
short-circuit detection. In the event that either a
thermal, short-circuit, or UVLO fault is de-
tected, the SP6137HV is forced into an idle state
where the output drivers are held off for a finite
period before a re-start is attempted.
Under Voltage Lock Out (UVLO)
Hiccup
The SP6137HV contains two separate UVLO
comparators to monitor the bias (V
CC
) and con-
version (V
IN
) voltages independently. The V
CC
UVLO threshold is internally set to 4.25V,
whereas the V
IN
UVLO threshold is program-
mable through the UVIN pin. When the UVIN
pin is greater than 2.5V, the SP6137HV is per-
mitted to start up pending the removal of all
other faults. Both the V
CC
and V
IN
UVLO com-
parators have been designed with hysteresis to
prevent noise from resetting a fault.
Soft Start
Upon the detection of a power, thermal, or short-
circuit fault, the SP6137HV is forced into an
idle state for 100mS (typical). The SS and COMP
pins are immediately pulled low, and the gate
drivers are held off for the duration of the
timeout period. Power and thermal faults have
to be removed before a restart may be attempted,
whereas, a short-circuit fault is internally cleared
shortly after the fault latch is set. Therefore, a
restart attempt is guaranteed every 100mS (typi-
cal) as long as the short-circuit condition per-
sists.
Thermal and Short-Circuit
Protection
“Soft Start” is achieved when a power converter
ramps up the output voltage while controlling
the magnitude of the input supply source cur-
rent. In a modern step down converter, ramping
up the positive terminal of the error amplifier
controls soft start. As a result, excess source
current can be defined as the current required to
charge the output capacitor.
IV
IN
= C
OUT
* DV
OUT
/ DTSoft-start
The SP6137HV provides the user with the op-
tion to program the soft start rate by tying a
capacitor from the SS pin to GND. The selection
of this capacitor is based on the 10uA pull up
current present at the SS pin and the 0.8V
reference voltage. Therefore, the excess source
can be redefined as:
IV
IN
= C
OUT
* DV
OUT
*10µA / (C
SS
* 0.8V)
Because the SP6137HV is designed to drive
large NFETs running at high current, there is a
chance that either the controller or power con-
verter will become too hot. Therefore, an inter-
nal thermal shutdown (145°C) has been in-
cluded to prevent the IC from malfunctioning at
extreme temperatures.
A short-circuit detection comparator has also
been included in the SP6137HV to protect against
the accidental short or sever build up of current
at the output of the power converter. This com-
parator constantly monitors the positive and
negative terminals of the error amplifier, and if
the V
FB
pin ever falls more than 250mV (typi-
cal) below the positive reference, a short-circuit
fault is set. Because the SS pin overrides the
internal 0.8V reference during soft start, the
SP6137HV is capable of detecting short-circuit
faults throughout the duration of soft start as
well as in regular operation.
Error Amplifier and Voltage Loop
As stated before, the heart of the SP6137HV
voltage error loop is a high performance, wide
bandwidth transconductance amplifier. Because
of the amplifier’s current limited (+/-150µA)
transconductance, there are many ways to com-
pensate the voltage loop or to control the COMP
pin externally. If a simple, single pole, single
© Copyright 2004 Sipex Corporation
Date: 5/25/04
SP6137HV Dual Supply, Synchronous Buck Controller
5
京公网安备 11010802033920号
EEWORLD
